<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>

    <style>
        div{
            width:1000px;
            height:700px;
            border:1px solid red;
            background-image:url("images/a.jpg");
            /*默认是全部平铺的* repeat/
        }
        .div1{
            /*水平平铺*/
            background-repeat:repeat-x;
        }
        .div2{
            /*垂直平铺*/
            background-repeat:repeat-y;
        }
        .div3{
            /*不平铺*/
            background-repeat:no-repeat;
        }
    </style>

</head>
<body>

<div class="div1"></div>
<div class="div2"></div>
<div class="div3"></div>

</body>
</html>